Copper-Based Bio-MOF/GO with Lewis Basic Sites for CO₂ Fixation into Cyclic Carbonates and C-C Bond-Forming Reactions

Several measures, including crude oil recovery improvement and carbon dioxide (CO₂) conversion into valuable chemicals, have been considered to decrease the greenhouse effect and ensure a sustainable low-carbon future. The Knoevenagel condensation and CO₂ fixation have been introduced as two principal solutions to these challenges. In the present study for the first time, bio-metal-organic frameworks (MOF)(Cu)/graphene oxide (GO) nanocomposites have been used as catalytic agents for these two reactions. In view of the attendance of amine groups, biological MOFs with NH₂ functional groups as Lewis base sites protruding on the channels' internal surface were used. The bio-MOF(Cu)/20%GO performs efficaciously in CO₂ fixation, leading to more than 99.9% conversion with TON = 525 via a solvent-free reaction under a 1 bar CO₂ atmosphere. It has been shown that these frameworks are highly catalytic due to the Lewis basic sites, i.e., NH₂, pyrimidine, and C═O groups. Besides, the Lewis base active sites exert synergistic effects and render bio-MOF(Cu)/10%GO nanostructures as highly efficient catalysts, significantly accelerating Knoevenagel condensation reactions of aldehydes and malononitrile as substrates, thanks to the high TOF (1327 h^-1) and acceptable reusability. Bio-MOFs can be stabilized in reactions using GO with oxygen-containing functional groups that contribute as efficient substitutes, leading to an expeditious reaction speed and facilitating substrate absorption.